Have you received a letter from the IRS? Go ahead and open it. I can't tell you how many clients come to me with unopened letters from the IRS. The clients simply don't want to see the "bad news." Next, if you are being audited, do not contact the IRS yourself. This is like representing yourself in a criminal matter. Remember, if you represent yourself in a criminal case you have a fool for a client. Same holds true for an IRS audit.
Call a qualified tax attorney if you get the IRS letter. Otherwise, if you start representing yourself you may cause damage to your case that is irreversable. Tax attorneys know how to deal with the IRS, and can establish a strategy for your case from the beginning to get the best result possible for your particular situation. This may include keeping you out of a criminal investigation. In the long run your savings with the IRS may exceed what the tax attorney will charge you.